This invention relates to improved apparatus and methods for detecting harmful substances, whether airborne or grounded, whether biological or chemical, which may pose an immediate or long term hazard to human life or health.
In my afore-cited co-pending applications, I have disclosed apparatus and methods for collecting various contaminantsxe2x80x94including vapors and particles, chemical or biologicalxe2x80x94from a large volume of air into a small volume of carrier liquid, so as to permit or facilitate rapid and ultra-sensitive detection of traces of hazardous or illicit substances which may be otherwise difficult to detect. The collected contaminants may be either dissolved by or suspended in the carrier liquid.
My earliest apparatus was intended mainly for the absorption of vapors by the carrier liquid and was therefore referred to as liquid-absorption air sampler. With subsequent use of the same apparatus for the collection of respirable particles, the term xe2x80x9cabsorptionxe2x80x9d became inappropriate, as the collected particles remain suspended in the carrier liquid without being dissolved therein. Such apparatus and methods will therefore be referred to herein as xe2x80x9cHTLAASxe2x80x9d for High-Throughput Liquid-Assisted Air Sampling, which applies to collected air contaminants which are either dissolved or suspended in a carrier liquid.
The present disclosures deal with several improvements and new potential applications of said apparatus and methods which extend the applicability of the HTLAAS technology to new uses and to previously unmanageable or borderline atmospheric conditions. Some of the new uses include collection of pathogen-bearing insects. For the sake of brevity, collected insects will also be referred to as xe2x80x9cparticulates,xe2x80x9d especially after being killed or incapacitated in a HTLAAS device.
The applicability of HTLAAS devices can be extended to various types of hazards which have been heretofore dealt with by other means in much less cost-effective ways. For instance, the present approach of the Environmental Protection Administration [EPA] is to monitor air, soils, and other areas for the presence of certain listed known or potential carcinogens, while possibly overlooking some unlisted ones. Therefore a single generalized method of monitoring for mutagenicity will not only be much more cost-effective than monitoring for a multiplicity of listed carcinogens but will also alert people to the presence of possible carcinogens which are not included in EPA""s list. In a recent well-publicized case, an increased incidence of brain tumors among workers in an Amoco laboratory could not be connected to the use or presence of any known carcinogen using existing analytical methods. The use of a water-assisted air sampler in conjunction with any of the known methods of testing aqueous solutions for mutagenicity, as claimed in my afore-listed co-pending applications, may thus provide a far more cost-effective and more powerful carcinogen alert than what is being used at present.
It is therefore another object of this invention to provide a cost-effective method and instrumentation for monitoring ambient air, soils, and other areas for mutagenicity.
A good measure of the performance of HTLAAS devices is the concentration factor F, which is proportional to the ratio of the concentrations in the liquid carrier and in air of the monitored air contaminant, hereinafter referred to as xe2x80x9canalyte.xe2x80x9d The concentration factor F is defined by the equation
F=xcex5S/vLxe2x80x83xe2x80x83[1],
where xcex5 is the sampler""s collection efficiency, S is its air sampling rate, and vL is the volume of liquid in which the analyte is collected.
Most of the previous work on concentrating airborne contaminants into a carrier liquid sought to maximize the collection efficiency and the air sampling rate within the limits imposed by size, weight, and power requirements. No serious attention was given to increasing the concentration factor F by minimizing vL. Yet by gathering the collected contaminants into a ten-fold smaller liquid volume we can achieve a 10-fold increase in their concentration within the liquid and hence in the overall sensitivity of the system.
It is therefore an object of this invention to greatly enhance the detection sensitivity of systems using liquid-assisted collection of airborne contaminants by minimizing the volume of the liquid into which said contaminants are gathered.
Present collection systems utilize primarily water-based carrier liquids, which have two important shortcomings, namely: [1] loss of water by evaporation during the sampling process; and [2] freeze-up of water at temperatures near or below 0 C. It is therefore also an object of this invention to overcome these shortcomings by substituting for the water an alternative carrier liquid having a much higher boiling point and lower freezing point.
Presently known water-assisted air-sampling systems have been used solely for detecting the presence of various of chemical or biological contaminants in ambient air. However, the same systems may also offer important advantages in the detection of concealed explosives, illicit drugs, or contaminated foods. It is therefore yet another object of my invention to provide an adapter that will permit collection by a liquid-assisted air sampling system of vapors or particles deriving from concealed hazards or illegal activities.
It is also an object of my invention to provide improved cost-effective apparatus and methods for capturing mosquitoes and other disease-transmitting insects in sufficient numbers to permit detection and identification of insect-borne pathogens.
Other objects of my invention are to provide an electronically programmable interface between a collector and a detector, so as to yield an automated or quasi-automated collection-detection system, to reduce the size and weight of the overall system, and to further enhance the system""s sensitivity by further increasing its collection efficiency and air sampling rate.
More objects of the invention will become apparent to professionals in the chemical and biological defense, law enforcement, health monitoring, disease control, industrial safety and hygiene, environmental, chemical, metallurgical, and related areas following perusal of the complete specification.
Briefly, the invention consists of extending the applicability of liquid-assisted air samplers to several new uses and to operation of such samplers under extreme climatic conditions. The new uses are effectuated in the following ways:
1. Providing generalized means and methods of detecting the presence of carcinogens in air, soils, and other areas by combining liquid-assisted air sampling with means for testing liquid samples for mutagenicity.
2. Providing means and methods of detecting the presence of hazardous or illicit substances or pathogens which may be buried in the ground or otherwise concealed or present in contaminated food at various stages of food processing, said means comprising a two-line probe such that one of the lines directs exhaust air from the sampler onto suspect surfaces so as to dislodge and blow off droplets, particles or insects therefrom while the other line draws some of them into the sampler. Variants of said two-line probe can also serve to collect lead, hexavalent chromium or other harmful substances and bacterial, fungal or viral pathogens from crumbling walls or floors.
3. Providing means and methods of capturing disease-transmitting insects and detecting and identifying insect-borne pathogens.
4. Extending the sampler""s operational range to extreme climatic conditions by substituting an organic low-vapor-pressure low-freezing-point carrier liquid, such as mineral oil, corn oil, or dimethyl sulfoxide, for the water in present liquid-assisted air samplers.
5. Extending the range of detectability of sampler-detector systems to lower air concentrations and smaller particle sizes by minimizing vL and increasing S and xcex5 of Equation 1. The minimization of vL is achieved by transferring the collected analyte from an organic carrier liquid into a tiny volume of water, taking advantage of the differences in the densities of these liquids. The increases in S and xcex5 are achieved by further improvements in sampler design.
6. The afore-said minimization of vL is preferably accomplished as part of an electronically programmable collector-detector interface which is geared for automated or quasi-automated air monitoring.